Air-cooled two-cycle internal-combustion engines provided with a scavenging pump



1955 JANTSCHKE AIR-COQLED TWO-CYCLE INTERNAL-COMBUSTION ENGINES PROVIDED WITH A SCAVENGING PUMP Filed April 3, 1952 United States Patent Oflic 2,102,533 Patented Feb. 22, 1955 AIR-COOLED TWO-CYCLE INTERNAL-COMBUS- TION ENGINES PROVIDED WITH A SCAVENG- lNG PUMP Leopold Jantschke, Stuttgart-Bad Cannstatt, Germany,

assignor to Dr.-lng. h. c. F. Porsche K.-G., Stuttgart- Zufienhausen, German Application April 3, 1952, Serial No. 280,333 Claims priority, application Germany April 20, 1951 13 Claims. (Cl. 12341.65)

' gines adapted for use in motor vehicles and agricultural tractors.

The primary object of the invention is to provide a compact engine structure, in which the auxiliary elements of the engine, such as the scavenging pump, the magneto, and the blower for cooling the working cylinder or cylinders are arranged in such a way as to provide a smooth engine structure in the form of a block which occupies a small space compared to its horse power and which is readily accommodated in a motor vehicle or tractor.

A further object of the invention is 'to provide a structure in which the auxiliary elements of the engine are constructed and arranged in a novel manner with respect to the working cylinder or cylinders of the engine.

In accordance with the features of the invention, the internal combustion engine structure comprises a working cylinder and head having cooling fins, a scavenging piston pump arranged in parallel with the working cylinder, the piston pump having a stroke substantially shorter than that of the working cylinder and arranged completely in the crankcase of the engine, a supporting bracket carried on the top of the scavenging pump opposite the working cylinder, and a blower carried by saidsupporting bracket for directing cooling air onto the working cylinder and the cylinder head of the engine.

It has been discovered, in accordance with the invention, that considerable space may be saved and an effective arrangement provided where the scavenging pump is arranged completely in the crankcase and provided with a cover which also supports the blower for directing the cooling air against the working piston. In this arrangement, the piston and cylinder of the scavenging pump are preferably constructed so that they have a diameter of from 1.4 to 1.8 times that of the working piston.- By making the scavenging pump of this size, it can be made relatively low so that it is readily accommodated in the crankcase, driven by the crankshaft and at the same time provide sufficient free space thereabove for the mounting of the cooling air blower, without having the latter extend above the working cylinder of the engine.

It has also-been discovered that, if the dynamo for the engine is built in the air blower casing and arranged so that it comprises a support for, or is combined with, the impeller of the blower, considerable further space is saved. In this arrangement, the impeller blower is mounted directly on the drive shaft of the dynamo and integrally includes a drive pulley.

In a preferred construction, the blower casing which surrounds the dynamo in spaced relation is adjustably arranged on its mounting bracket so that the tightness of the driving belt may be readily adjusted. In this connection the means for driving the blower preferably comprises a V-belt pulley, which is.driven at a higher speed than the crankshaft of the engine, thereby permitting the use of relatively smaller pulleys than otherwise would be necessary. I I

Preferably the means for driving the scavenging pump from the crankshaft comprises an integral forged crank pin, counterweight and driving gear secured to one end 2 of the crankshaft in the crankcase, thereby providing a very effective space-saving drive forthe scavenging which are described more in detail hereinafter in connection with the accompanying drawings showing one embodiment of the invention and comprising a part of this application.

In the drawings,

Fig. 1 is a vertical central longitudinal sectional view of an air-cooled, single-cylinder, two-stroke cycle internal combustion engine, in which the parts are constructed and arranged in accordance with the invention; and

Fig. 2 is a front elevational view of the internal combustion engine shown in Fig. 1.

Fig. 3 is a broken view partly in section taken on the line 3-3 of Fig. 1.

Referring to the drawings, the improved engine comprises a working cylinder 1 supported on an engine crankcase 2, in which a crankshaft 3 is mounted. The driving end of the crankshaft extends to the right and serves as the drive for the engine and on which is mounted a fly wheel 4 within the crankcase 2. At the other (front) end of the crankshaft in the crankcase, a forged block 5 is fixed to the end of the crankshaft 3 by means of a stud bolt 6 threaded into the end of the shaft. The forged block 5 is preshaped to provide a crank pin 7 for a connecting rod 8 connected to a piston 16 operating in a scavenging pump cylinder 9 fitted in a cylindrical portion of the crankcase having fins 9'. The onepiece block 5, in addition to the projecting crank pin 7, also includes a counterweight 10 and a peripheral gear 11 for driving the auxiliary devices or machines included as apart of the internal combustion engine.

The front of the crankcase includes a removable cover plate 2 having therein a bearing structure, in which a starting shaft 15 is mounted in axial alignment with the crankshaft 3. The shaft 15 includes a cam 12 for operating a fuel injection pump or equivalent means, not shown. The inner end of the shaft 15 is provided with a disc portion 14 having an oil. center opening or slot therein engaged by a driving crank pin 13 projecting axially from the crank pin 7. In this structure, the disc 14 serves as a crank for rotation of the shaft 15, while the engine is running, or for rotation of the engine crankshaft in starting the engine, by applying the usual hand starting crank (not shown) to the front end of the shaft 15 so that it engages the conventional type pin therein as shown in Fig. 1. The position of the disc 14 with respect to the crank pin 7 and the connecting rod 8 is such that the connecting rod 8 is retained on pin 7 by air to the working cylinder 1.

the disc 14. l

The scavenging pump, which is mounted in front of and parallel to the working cylinder 1, is arranged with a short stroke compared to that of the engine piston, the diameter of the scavenging piston 16 preferably being from 1.4-to 1.8 times that of the working piston 17 so that the pump is arranged relatively low in the overall structure and can be entirely accommodated in the crankcase, while at the same time having adequate capacity for delivering the required volume of scavenging The working piston 17 is driven by a connecting rod 17.

The relative positions of the pump cylinder 9 and the working cylinder 1 are shown in Fig. 1, and this arrangefor accommodating certain of the auxiliary devices necessary for the effective operation of the engine. Accordingly, the pump cylinder 9 is provided with a cylinder head 18 made integral with a loop type supporting bracket 19. If desired, the bracket'19 may be made separately and attached to the cylinder head 18. A blower for supplying cooling air to the cylinder 1, including a cylindrical casing 23, is mounted on the-front of the cylindrically-shaped support 19 by means of screw bolts 20, 21, and 22. The blower also includes a front grill 23' fitting l the front of the casing 23, an impeller wheel 24, and a hollow casing 25 directly in back of the hub of the impeller 24. The impeller 24 includes blades 24' mounted v on the periphery of the hub within the casing 23, whil -the hollow casing 25 is mounted in fixed position axially of this hub and together they provide a housing for a dynamo or generator 26, for generating electricity, which is secured therein by means of a spacer ring 27 and screws 28. In this construction, the dynamo 26 is arranged so that its shaft 29 extends through the hub of the blower impeller wheel 24 and is rotatably coupled thereto. Moreover, the impeller wheel 24 is preferably constructed as shown, in one piece so that it integrally includes a V-belt pulley 30, which is used for driving the impeller wheel 24 and the shaft 29 of the dynamo 26.

The arrangement of the blower and dynamo the position shown on top of the scavenging pump and directly in front of the working cylinder provides a very compact and block-shaped structure. The hollow support 19 directs the cooling air from the blower directly on the cooling fins 1 of the working cylinder 1 and on the fins 38' of the working cylinder head 38.

The gear wheel 11 on the block meshes with a gear of a change-speed gear transmission, not shown, which drives a V-belt pulley 33 (Fig. 2), secured on the shaft of the engine regulator, not shown. The change-speed gear transmission is arranged to provide a higher speed for the pulley 33 than that of the crankshaft 3 so that, as stated above, the pulleys on the engine may be considerably smaller than otherwise would be necessary. The change-speed transmission gear system may include .a relatively small gear 33' on the shaft on which the pulley 33 is mounted and at least one other gear 11' meshing with the gear 11. The V-belt pulley 33 drives a V-belt 32 which extends around the V-belt pulleys 30 and 31 as seen in Fig. 2 of the drawings. The pulley 31 is used to drive an oil cleaning device of a known type for cleaning the oil used in the engine, which device may, for example, include a centrifugal cleaner, but which forms no part of the present invention.

The tightness of the V-belt 32 may be adjusted by means of the structure provided in connection with the flange 35 of the casing 23, by which this casing is secured to the face of the bracket 19. This flange 35 includes a slot 36 for the screw bolt 20 and a slot 37 for the screw bolt 22. The tightness of the V-belt 32 is adjusted by loosening the screw bolts 20, 21 and 22 and pivoting the blower casing 23 and flange 35 on the bolt 21 by adjusting a setting screw bolt 36' to pivot the casing in the desired direction on the bolt 21, after which the screw bolts 20, 21, and 22 are tightened.

It will be understood that the pump cylinder 9 and the working cylinder 1 will include the necessary ports and passages for scavenging air and exhaust gases, some of which are shown in Fig. 1 of the drawings. Furthermore, a fuel admission valve is shown in the cylinder head 38 and other elements are shown in the drawings, all of which form no part of the present invention.

The engine construction and arrangement shown in the drawings and described above, including the auxiliary devices of the engine, provides a novel block-like, unbroken, compact shape which occupies a relatively small space compared to its power output, so that it can be easily assembled and dissembled and readily mounted in the place provided therefor in automotive vehicles and tractors. It will be readily seen from the front showing in Fig. 2, that the dynamo and scavenging pump are not readily discernible from the outside. The working cylinder 1 and its piston head 38 are located approximately at the height of the cooling blower, so that effective cooling of the working cylinder is secured and at the saglei time a compact structure and appearance is provi e While the internal combustion engine of the present invention has been described in connection with a single cylinder two-cycle engine, the features of the invention can be appropriately applied to air-cooled engines having two or more working cylinders. What is claimed as new is:

1. In an air-cooled two-cycle internal combustion engine, including a crankcase, a finned engine working cylinder and a finned cylinder head therefor extending above the crankcase, a piston pump for supplying scavenging air to the working cylinder mounted in parallel with the working cylinder, a cover on the scavenging pump, a

support carried by said cover, and a blower mounted on said support having its discharge outlet adjacent to and directed toward the finned working cylinder and cylinder head of the engine.

2. an air-cooled engine as claimed in claim 1, in which the piston of the scavenging purn has a diameter of from 1.4 to 1.8 times that of the-diameter of the piston in the working cylinder of the engine.

3. An air-cooled engine as claimed in claim 1, in which said blower includes an axially arranged structure, and a dynamo for the operation of the engine mounted in said axially-arranged structure.

4. An air-cooled engine as claimed in claim 1, in which said blower includes a structure comprising an engine dynamo mounted axially with respect to the blower, said dynamo having a drive shaft, and said blower having an impeller mounted on said drive shaft.

5. An air-cooled two-cycle internal combustion engine as claimed in claim 1, including a V-belt pulley for rotating the impeller of the blower, and means for driving said pulley by the engine at a higher speed than that of the crankshaft of the engine.

6. An air-cooled engine as claimed in claim 1, in which the support carried by the cover of the scavenging pump comprises a cylindrically shaped support, one end of which faces toward the working cylinder of the engine, said blower including a cylindrical casing adjustably mounted on the end of said support opposite the working cylinder of the engine, said blower including an impeller axially arranged in said casing for driving air through the casing and the support onto the finned working cylinder and cylinder head of the engine.

7. An air-cooled engine as claimed in claim 1, in which the cover of the scavenging pump and said support comprises an integral structure in which the support is a cylindrically shaped loop, the axis of which extends toward the working cylinder of the engine.

8. In an air-cooled two-cycle internal combustion engine, including a crankcase, a finned engine working cylinder and a finned cylinder head therefor extending above the crankcase, a piston pump driven by the engine for supplying scavenging air to the working cylinder, said pump being mounted in parallel with the working cylinder, a head for said piston pump, a supporting bracket carried by the head of the piston pump adjacent to the working cylinder of the engine, a blower including an outer cylindrical casing mounted on said supporting bracket and arranged to discharge air against the working cylinder and cylinder head, said blower including an interior hollow casing spaced from and supported by said outer casing, said casings providing an annular passageway for the flow of air, a dynamo for the operation of the engine mounted in said interior casing and including a drive shaft projecting therefrom, a cup-shaped hub fixed to said drive shaft and extending over the front end of the dynamo, the rim of the hub facing the front rim of said interior casing, and impeller blades on said hub.

9. An air-cooled engine as claimed in claim 8 in which said cup-shaped hub includes an outwardly and rearwardly extending portion immediately surrounding the shaft of the dynamo, and an outwardly and forwardly extending flange on said portion of the cup-shaped hub adapted to provide a V-belt pulley integral with said hub.

10. An air-cooled engine as claimed in claim 8 in which said supporting bracket comprises a cylindrically shaped support the axis of which dproints toward the working cylinder of the engine and ough which the air from the blower is adapted to flow.

11. An air-cooled engine as claimed in claim 8 in which said supporting bracket comprises a cylindrically shaped member, the axis of which extends toward the working cylinder of the engine, and means for adjustably supporting the outer casing of the blower on the end of said bracket support opposite the working cylinder of the en- An air-cooled engine as claimed in claim 8 in which the hub of the blower impeller includes a V-belt pulley scavenging air to the working cylinder and mounted in parallel with the working cylinder, said pump including a piston and cylinder, a crankshaft mounted in the crankcase, a working piston mounted in the working cylinder and operatively connected to the crankshaft, means op- 5 crank pin, a in mounted on said crank pin and extending 10 axially there mm, a starting shaft for the engine mounted axially with respect to and in front of said end of the crankshaft of the engine, a disc mounted axially on the end of said starting shaft facing toward the crankshaft and having an off-center opening in ,which said extending 16 pin is engaged, whereby rotation of said starting shaft is adapted to rotate the crankshaft of theengine.

References Cited in the file of this patent UNITED STATES PATENTS 1,408,753 Long Mar. 7, 1922 1,511,707 Burtnett Oct. 14, 1924 FOREIGN PATENTS 214,683 Great. Britain Apr. 23, 1924 249,532 Great Britain July 29, 1926 430,490 Great Britain June 17, 1935 France May 15, 1939 

